Carbon nanotubes (also referred to as carbon fibrils) are seamless tubes of graphite sheets, first discovered as multi-layer concentric tubes or multi-walled carbon nanotubes and subsequently as single-walled carbon nanotubes. Carbon nanotubes have shown promising applications including nanoscale electronic devices, high strength materials, electron field emission, tips for scanning probe microscopy, and gas storage.
Generally, single-walled carbon nanotubes (SWNTs) have advantages over multi-walled carbon nanotubes for use in these applications because they have fewer defects and are therefore stronger and more conductive than multi-walled carbon nanotubes of similar diameter. Moreover, single-walled carbon nanotubes with substantially uniform alignment have been shown to have further advantages over non-aligned nanotubes. For example, vertical single-walled carbon nanotubes (V-SWNTs), have attracted particular interest for some of the above applications.
In addition to their multiplicity and alignment, other physical parameters of carbon nanotubes also have important implications in their utility. For example, the level of purity is often vital to the applicability of carbon nanotubes in electronic devices. The control of physical dimensions of carbon nanotubes, such as diameter, length and chirality, is also of benefit, for example, in hydrogen storage applications. Nevertheless, current methods of preparation often suffer from narrow parameter windows and/or low reproducibility.
Thus, the availability of single-walled carbon nanotubes, particularly vertical single-walled carbon nanotubes, in quantities and with attributes necessary for practical technology is still problematic. As a result, processes for the production of high quality single-walled carbon nanotubes are still needed.